Incongruence between morphotypes and genetically delimited species in the coral genus Stylophora: phenotypic plasticity, morphological convergence, morphological stasis or interspecific hybridization?

Abstract

BackgroundMorphological data suggest that, unlike most other groups of marine organisms, scleractinian corals of the genus Stylophora are more diverse in the western Indian Ocean and in the Red Sea than in the central Indo-Pacific. However, the morphology of corals is often a poor predictor of their actual biodiversity: hence, we conducted a genetic survey of Stylophora corals collected in Madagascar, Okinawa, the Philippines and New Caledonia in an attempt to find out the true number of species in these various locations.ResultsA molecular phylogenetic analysis of the mitochondrial ORF and putative control region concurs with a haploweb analysis of nuclear ITS2 sequences in delimiting three species among our dataset: species A and B are found in Madagascar whereas species C occurs in Okinawa, the Philippines and New Caledonia. Comparison of ITS1 sequences from these three species with data available online suggests that species C is also found on the Great Barrier Reef, in Malaysia, in the South China Sea and in Taiwan, and that a distinct species D occurs in the Red Sea. Shallow-water morphs of species A correspond to the morphological description of Stylophora madagascarensis, species B presents the morphology of Stylophora mordax, whereas species C comprises various morphotypes including Stylophora pistillata and Stylophora mordax.ConclusionsGenetic analysis of the coral genus Stylophora reveals species boundaries that are not congruent with morphological traits. Of the four hypotheses that may explain such discrepancy (phenotypic plasticity, morphological stasis, morphological convergence, and interspecific hybridization), the first two appear likely to play a role but the fourth one is rejected since mitochondrial and nuclear markers yield congruent species delimitations. The position of the root in our molecular phylogenies suggests that the center of origin of Stylophora is located in the western Indian Ocean, which probably explains why this genus presents a higher biodiversity in the westernmost part of its area of distribution than in the "Coral Triangle".

Species delimitation in the coral genus Goniopora (Scleractinia, Poritidae) from the Saudi Arabian Red Sea

“…Direct sequencing and subsequent phase analysis in a Bayesian framework revealed that all analyzed samples host either one or two dominant types of ITS region sequences, a situation previously reported in other coral genera (Flot et al, 2006(Flot et al, , 2008a(Flot et al, , 2011Schmidt-Roach et al, 2012). Moreover, most ITS region types that cooccurred in some Goniopora colonies were found to be harbored alone in other specimens, suggesting that these variants might be allelic and each samples might be either homogeneous or heterogeneous for this molecular locus (Flot et al, 2006(Flot et al, , 2011 as observed for single-copy nuclear genes such as ATPsβ and CalM.…”

“…Unfortunately, scleractinian morphology exhibits extensive phenotypic plasticity, high variability, and/or evolutionary convergence that often obscure natural patterns of evolution (e.g., Gittenberger and Hoeksema, 2006;Fukami et al, 2004;Todd, 2008;Flot et al, 2011;Budd et al, 2012). The integration of molecular tools with morphological analyses has proven to be powerful in clarifying misleading and complex phylogenies, with recent examples in the genera Pocillopora (Schmidt Roach et al, 2014), Psammocora (Stefani et al, 2008;Benzoni et al, 2010), and Desmophyllium (Addamo et al, 2016).…”

“…Moreover, most ITS region types that cooccurred in some Goniopora colonies were found to be harbored alone in other specimens, suggesting that these variants might be allelic and each samples might be either homogeneous or heterogeneous for this molecular locus (Flot et al, 2006(Flot et al, , 2011 as observed for single-copy nuclear genes such as ATPsβ and CalM.…”

Assessing hidden species diversity in the coral Pocillopora damicornis from Eastern Australia

“…The Pocillopora damicornis sensu lato morphological variants identified here are clearly associated with genetically distinct lineages, thus reinforcing the growing literature revealing cryptic speciation in a wide variety of coral groups and within so-called morphologically variable taxa, for example, Montipora spp. (Stobart and Benzie 1994), Montastraea annularis (Medina et al 1999), species within the Faviidae (Nunes et al 2008), and species within the Poritidae (Forsman et al 2009;Flot et al 2011). It should be noted, however, that while our results demonstrate that accepted ecomorphs of P. damicornis may represent different species, we do not completely discount the influence of eco-phenotypic variation in pocilloporid diversity and systematics.…”

Seriatopora Diversity Preserved in Upper Mesophotic Coral Ecosystems in Southern Japan

“…A GTR substitution model was used with a 6 gamma categories and Stylophora sp. as outgroup with ITS2 and ORF sequences from the specimen 04Oki195 (JN559077 and JN558888, Flot et al, 2011). In addition the 6 Seriatopora sequences from Nakajima et al (2017) were included in the ORF tree for comparison.…”